Factors to Consider When Designing an RGB Pixel Matrix

Over the years we at HolidayCoro have been asked why we only sell a single pixel matrix product - our 18" x 24" pixel with either 150 or 162 pixels.  Well, actually, we've produced a fair number of custom matrix based panel items for customers over the years and the main reason we don't offer all these variations for sale is because each project is so different.  The article hopes to provide information on factors that we consider when working with customers on designing a pixel matrix and hopefully this will help those building their own or working with us to custom produce one.

• What exactly is the purpose of the pixel matrix?
• Is this matrix intended to be dense enough that viewers will be able to see objects scrolling or displayed on it such as text, icons or logos?  
• What is the viewing distance from the matrix to the viewer?  If you've ever looked at a big screen TV up close, you can understand the relationship the size of the pixels (lights) have to the distance they are being viewed from.
• What is the viewing angle?  A curve pixel panel (such as a pixel megatree) can look odd if all the pixels in the matrix are not visible to the viewer.
• What is the shape of the matrix?  Is the matrix a cone, in the case of a pixel megatree, where the pixels at the top are in a much higher density than those at the bottom of the tree?  Is the matrix cylindrical?  flat? concave or convex?  All these designs have an effect on the final output, pixel density and mounting methods.
• Technical factors to consider include:
• Number of pixels - This is an important factor to consider and the number shouldn't be random - it should be based on the design requirements.  Look closely at how many pixels you'll need and their spacing from each other.  If needed, build a sample mock-up and view it from the distance and angle you expect your viewer to view it from. 
• Pixel height and width - Also consider how many pixels you may need to display certain items such as a text font which often require a 5x8 pattern.  Again, keep in mind that you will also need to have the pixels close enough that the human eye can make out the pattern - just because it might look good in the sequencing software doesn't mean that will translate into the real world.  
• Multi-Panel Alignment - If the matrix will be comprised of several panels, be sure to carefully consider the spacing within a panel and how it relates to the spacing induced between two adjoining panels.  This may mean that you will need to increase the center-to-center spacing of the lights to match that of the panel-to-panel gap.
• Mounting or support - An important part of any matrix is how you will mount it - because a matrix tends to be a flat area (excluding pixel megatrees), you'll need to think hard about what system you'll use to mount the substrate on to which the pixels are mounted. If that surface catches the air, there could be problems with it blowing over or toppling the support structure.  Also consider that you'll need to store this mounting system in the off-season - so if the panels need to go into an attic, consider the opening going to the attic.
• Substrate mounting - In most cases, you'll need to mount your pixels to a substrate - not only to support them but to maintain a clean and even spacing - there isn't anything worse than a matrix that has mis-aligned pixels.  How you mount those pixels can vary - it could be holes in coro like we do at HolidayCoro or it could be screwed or glued to wood slats or plywood - this all depends on your pixel type.
• Pixel type - The type of pixel you select will often be a by-product of the distance and viewing angle of the people viewing your matrix.  These pixels could be in a strip form, node form or module form and each has it's pros and cons and there is no one pixel that is best suited for all matrix types.
• Channels - Keep in mind that you'll often have many, many DMX channels on a matrix display and it makes sense to select pixel counts that fall within a set number of DMX universes - so don't design a pixel display that requires 180 pixels (18 wide by 10 high) if it could have been done in 163 pixels (18 wide by 9 high) which fits neatly into a single DMX universe and thus saves you a controller or controller output and also makes your sequencing easier to setup and manage.
• Repairs - Factor in that pixels DO fail and that you'll need to fix them.  So consider how easy it will be to remove and replace pixels.
• Cost / Budget - A matrix can grow in cost quite quickly when you factor in hundreds to thousands of pixels, so be sure to ask yourself the overall value of the matrix and how well it accomplishes its goal.  If this is just for announcing the radio station and song titles, a simple matrix will do - if you need to scroll logos or animations, you'll need a larger and more expensive matrix.
• Big isn't always better - Since pixels have come down in price and complexity, we've seen a number of pixel matrix panels (and pixel megatrees) in displays that just completely over-shadow and "hog" the display.  We believe that a well balanced display should be the ideal and that one mega-element can leave your audience so fixated on one area that they fail to see other areas and animation. 
• Software & Sequencing - Building a matrix panel is only one part of the process and the other major part is generating the sequencing for that panel.  Since it is nearly impossible to "hand" sequence matrix displays, you'll want to consider applications like LightShow Pro's matrix animator or Light-o-Rama's Superstar lights or other freeware applications that have been coming into the market.  You may even want to design your pixel display hardware, then start sequencing it before you buy or build it to evaluate how complex it will be to sequence the matrix.